Crude oils may contain considerable amounts of paraffins tat vary according to the nature of the crude oil. At the temperature of the wells, these paraffins dissolve in the crude oil and are in liquid state. When the crude oil rises to the surface, and mainly during its transportation and storage, its temperature decreases and the paraffins crystallize in the form of scales or needles. The crystallization of the paraffins decreases the flow properties of the crude oils and their pumpability. At the same time, the heavier paraffins agglomerate in the form of nets on the cold walls and cause the formation of deposits in the conduits and reservoirs. The accumulation of these deposits results in considerable losses of production. In narrow passages, there is even the risk of a complete obstruction.
Numerous process have been proposed for the solution of the aforesaid problems. There are mechanical processes consisting in scraping the inner walls of conduits and reservoirs. It is evident that, aside from the high cost of this process, its use is often impossible as well as impractical.
There has likewise been suggested the use of so-called paraffin-inhibitor additives the purpose of which is to delay the crystallization of the paraffins and above all to prevent the agglomeration of crystals formed on the walls.
Paraffin inhibitors are usually olefin polymers or copolymers. But the polymer products involve a certain number of inconveniences. Their polymeric structure makes them sensitive to shear. They serve well as crystallization inhibitors when the crude oil is not subjected to shear, but the forces exerted in the conduits during transportation of the crude oil by pumping cancel their effects.
The object of this invention is therefore to provide a process that remains effective during both the storage and the transportation of crude petroleum. The additives according to the invention make it possible, on the one hand, to maintain in dispersion the whole range of paraffins, improving the flowing properties of the crude oils and, on the other, to prevent the deposit of the heavier paraffins on the walls.